Rod Laver Arena | 11 p.m. TuesdayAndrey Rublev vs. Daniil MedvedevAndrey Rubley and Daniil Medvedev secured the ATP Cup for Russia earlier this month, with neither player losing a singles match throughout. In their three meetings on the ATP Tour, Medvedev has come out on top each time, including in the quarterfinals of the U.S. Open in September.This may be Rublev’s chance to finally overcome his friendly rival. He has looked particularly dominant, not dropping a set throughout the tournament. His match against Casper Ruud ended after only two sets when the Norwegian withdrew with an injury. Going into the quarterfinals, Rublev has led the field in both percentage of first service points won and second service points won, a sign of how hard it has been for opponents to break his serve.Medvedev has also been playing well, aside from a chaotic, disorganized third round match against Filip Krajinovic. He has now won 18 matches in a row, with his last loss coming in October at a tournament in Vienna. Although the fast surface fits Medvedev’s flat baseline shots, Rublev’s open stance is well suited in defense, and we’re sure to see many dynamic, aggressive point.Rod Laver Arena | 3:30 a.m. WednesdayRafael Nadal vs. Stefanos TsitsipasRafael Nadal, the No. 2 seed, has moved smoothly through the first four rounds, no surprise for a player with 20 Grand Slam titles. Although Nadal won his only Australian Open title over a decade ago, he has reached the finals on four other occasions since, and is a clear favorite in his half of the draw to do so again. Nadal’s powerful topspin shots are well-suited to clay courts where he can drag opponents around with tightly angled shots. Nadal’s ability to exploit his opponent’s weaknesses with relentless pressure can break most players on their best days.Stefanos Tsitsipas, the ATP finals winner in 2019, is a study in unpredictability. The fifth seed has a capable all-court game, but lacks the consistency to execute match after match. The 22-year-old has worked to improve this aspect of his game, but needed five sets to push back unseeded Thanasi Kokkinakis in the second round. After receiving a walkover in the round of 16, Tsitsipas will be well rested and hoping for an advantage against one of the most mentally tough players on tour.